Carburetor



April 13, 1943. o, 1.. GARRETSON CARBURETOR Filed Sept. 22, 1941 FUEL lNVENTOR O. L. GARRETSON BY M w ATTQR EY .tion as indicated -tnbe and is placed in views in terms CARBUBETOE Owen L. Garretson, Detroit,

Phillips Petroleum Company,

Delaware Mich, gnor to a corporation of Application September 22, 1941, Serial No. 411,929 1 Claim. (c1. eel-: 9)

. This'invention relates to carburetors; and more particularly it relates to a carbureting device for use with internal combustion engines wherein volatile liquid fuels of essentially any vapor pressure, ranging from the vapor pressure of present day commercial pressure fuels as natural gasoline and liquefied petroleum gases, may be used.

An object of this method and apparatus for carbureting very volatile or high vapor pressure liquid fuels or liquefied petroleum gases for use in internal combustion engines.

Another object of this invention is to provide a carburetor of simple and compact design, with few adjustments for use with high vapor pressure liquid fuels.

Another object of this invention is to provide a carburetor for use with high vapor pressure liquid fuels which will permit the metering of liquid fuel to give an air-fuel ratio essentially in accordance with throttle requirements.

Still'another object of this invention is to pro vide a method and apparatus for carbureting high vapor pressure liquid fuels for use in aircraft engines as well as in automotive engines.

Yet another important is to furnish a carburetor for use with high vapor pressure fuels for automotive and aircraft engines which will be sensitive, rapid in response to the throttle and free from premature ebullition or vapor lock.

Still other objects and advantages will be apparent to those skilled in the art from a careful study of the following detailed disclosure.

The figure represents one embodiment of my invention directly applicable for use combustion engines where high vapor pressure hydrocarbons or'mixturesthereof are used as Referring to the figure, numeral i represents the air inlet tube with the air flowing in the direcby the arrow. The air flows in accordance to intake 'manifold suction as controlled by the butterfly throttle valve 2 Constriction 3 in the air inlet tube serves as a Venturi the air. inlet line just prethrottle 2. Passing through the thickened've'nturi wall is an opening 5 for connectinggchamber E to the air inlet tube I. Diaphragm 1 of conventional design separates chamber 5. Tube It co ects chamber 6 with the air inlet l for equalization of pressure or more specifically for maintaining the air pressure in object of this invention with internal gasoline to such high .vapor invention is to provide a chamber 6 equal to-that 0f the incoming air in the air inlet. To one side of the diaphragm l is attached rigidly the push pin it which extends from the said diaphragm through chamber '5 and opening d, across the throat of venturi t,

conventional adjusting apparatus 5. The tension v in said spring is so adjusted that the synthetic rubber face ll of valve head it contacts the valve seat l6 therebypreventing flow of liquid fuel from chamber it into the vaporizing portion it of the air inlet during periods of inoperation.

In some cases spring it be in compression of direction of'air fiowto the chamber 6 from said opening 4 in air chamber B. By

in chamber 5 is reduced slightly, for example,

to partially balance liquid pressure on valve it The valve is then held closed at rest by liquid pressure. Pipe 26 is the fuel line for the conduction of liquid fuel from the fuel. storage tank, not shown, to the carburetor, and terminates in compartment 2| which may be maintained under the same pressure as the said fuel storage tank. However, a pressure slightly above the fuel vapor pressure is ordinarily preferred to prevent vaporization through valve 23 and for this purpose a pump may be employed. Tube 22 connects liquid fuel pressure chamber it with liquid fuel feed chamber l8 and has a valve or orifice 23, fuel flow therethrough establishing a pressure differential on diaphragm l5 urging valve it closed and balancing the opposing force exerted by. diaphragm l. 7

Tube 2t connects chamber 5 with the air inlet tube at a point on the downstream side of the throttle valve 2 and serves to increase suction on diaphragm 8, insuring proper flow of fuel to the inlet tube during idling when low pressure exists on the downstream side of the throttle valve. Valve or orifice 25 is inserted in this tube 24 for adjustment ofthe amount of suction for motor idling. I

In the operation according-to my invention, air

is drawn through the air inlet tube I by suction from the intake manifold, not shown, and flows through my'carburetor in the directions as shown by the arrow. when the air passes the constriction' in the air passage or venturi t, suction set up by said venturi is communicated through the wall of the venturi intothe such suction the air pressure from a fraction of 1 to say 20 or 25 inches of water. Chamber 6 is maintained at essentially atmospheric or nearly atmospheric pressure by the air pressure equalizer tube III which connects said chamber 6 with the carburetor air intake I. In case an air cleaner is used, the pressure in the air intake l and chamber 6 will be slightly lower than atmospheric due to resistance to air flow through the cleaner. This slight pressure drop or differential is immaterial in the operation of my invention, the important point being to maintain essentially equal pressures in said chamber 6 and air inlet l.

The pressure of air in chamber 5 being reduced by the action of the intake air passing through the ventur causes a pressure differential to act on diaphragm I, causing the latter to move in the direction of the reduced pressure. This slight diaphragm movement is transmitted through the rigid push pin ll causing valve. IE to open, thereby permitting flow of liquid fuel from liquid fuel feed chamber IB. The liquid fuel on passing through the slight opening of valve l6 experiences a pressure reduction which causes ebullition and vaporization. The liquid and newly formed vapor pass through opening l3 into tube l2 and thence into the air stream in the vaporizing portion 19 of the air inlet tube for vaporization and mixture with the air. The flow of the thus formed combustible fuel mixture into the intake manifold and thence into the cylinders is controlled by the butterfly throttle valve 2 of conventional design.

Line 20 carries liquid fuel from the fuel supply tank, not shown, to my carbureting device. Fuel in this fuel tank may be maintained under atmospheric pressure, its, own vapor pressure, or under superatmospheric pressure.

Liquid fuel from the said supply tank enters the carburetor in the liquid fuel pressure chamber 2|, and flows then through tube 22 into the liquid fuel feed chamber l8. Valve or orifice 23 in tube 22 restricts or controls the fiow of liquid fuel from pressure chamber 2| to feed chamber iii to maintain a pressure diiferential between these two fuel chambers when liquid fuel is flowing through valve l6. This pressure differential acts on diaphragm I5 tending to close valve I6 and reduce the flow of liquid fuel. The magnitude of the pressure differential is' a function of the rate of 'fuel flow. However, in actual operation, the above explained'air pressure differential drop is necessitated by the fact that only a small pressure drop is available for actuating diaphragm I, and the diaphrasms l and I5 are of essentially the same size in the preferred embodiment of my invention. However, it is not necessary that the said diaphragm be the same size, since the air pressure actuated diaphragm 1 may be some larger or even considerably larger in area than the liquid actuated diaphragm l8, or may even be some smaller but preferably not appreciably smaller and yet impart suflicien't force to the push pin .II to operate the fuel metering valve l6.

In starting an engine equipped with my car-' buretor as herein disclosed, the following steps of operation or actuations will take place. -When the motor is turned a partial vacuum is set up within the intake manifold, not shown, and communicated to the air inlet of my carbureting device. The rush. of intake air through the venturi 3 sets up a suction through opening 4 which reduces the pressure in chamber 5, thereby causing diaphragm 1 to move in the direction of the lower pressure, thereby opening valve I6. A butterfly choke may be employed between line l0 and the venturi to increase the pressure differential for starting. As long as there is no flow of liquid fuel through valve 16, no pressure differential operates against diaphragm l5, and the air operated diaphragm causesvalve IE to open. Upon opening of this fuel valve liquid passes therethrough and a pressure differential is set up between liquid fuel pressure chamber 2| and liquid fuel feed chamber I8 opposing the force of the air diaphragm. If the motor does not start upon the first turnover, as soon as it comes to rest, no pressure differentials exist and tension spring 8 closes metering valve l6 and fuel ceases to fiow. If following the turnover or cranking operations as described, the engine starts, the rush of air through venturi 3 is increased, pressure differential on diaphragm l is increased tending to meter a larger volume of liquid fuel through valve l6 and similarly a greater pressure g the said pressure differentials reach an equilibacting on diaphragm I balances the pressure differential set up on diaphragm IS. The net result of this combined operation is to maintain an equilibrium in which the fuel valve is maintained open to an extent dependent on air ve locity through inlet tube 1. The diaphragms are so selected or manufactured that they possess the proper rigidity to permit operation under stress of the relatively low pressure differentials which exist in my carbureting device.

Spring 8 is so adjusted by adjuster 9 which may be of conventional design, that during periods of inoperation the valve I6 is closed,'thus permitting positive in its action when properly adjusted, and yet not of sufficient strength to interfere with the gine.

'no flow or leakage of fuel. The spring must be operation of the diaphragms I and I5 and valve IS. The tension or compression adjustment of spring 8 will depend to a great extent on the relative size of valve orifice l6, diaphragms and vapor pressure of the fuel. In some cases the spring may be omitted entirely.

Valve or orifice 23 in tube 22 is so adjusted that there is only a relatively small pressure drop therethrough. This relatively small pressure 15 rium and the metering valve I6 remains fixed in position allowing a fixed amount of liquid fuel to pass if there is a constant air flow into the en- These conditions remain constant until the throttle valve 2 is changed by the operator when a new set of equilibrium conditions is reached in accordance with the flow of air through the venturi 3, establishing a new valve position.

Line 24 connects chamber 5 and the air inlet tube I on the downstream side of the throttle 2 for motor idling. During the idling operation of the motor the throttle valve is nearly closed, thereby producing small suction in the venturi, which may be insufficient to overcome the action of the loading spring and give accurate metering at low speeds. Low pressure existent on the downstream side of the throttle valve when the valve is nearly closed is utilized to supplement venturi action and provide adequate metering during idling. Adjustment of suction through tube 24 is obtained by regulation of valve 25.

To make the carburetor responsive to the throttle'and to the suction through tube 24 for idling the volume of chamber land the cross sectlonal'area of opening 4 should be as small as possible and yet allow free working of the diaphragm I and passage of air through the opening 4.

Opening i3 through the Venturi wall and tube l2 attached thereto are of relatively small cross section so that the liquid fuel will be converted to vapor mainly in the mixing portion [9 of the air intake tube l.

The valve head I4 is equipped on its underside or face with a material such as synthetic rubber, in order to make an effective closure when the motor is not in operation. This material need not necessarily be synthetic rubber, and I do not wish to limit myself in this respect, since various metals and other materials which are not soluble in hydrocarbons or do not exhibit the property of imbibition or smelling in the presence of such liquids, and yet will make an effective shut-01f or seal, may be used.

Valve It should be made as small as possible in order that the relatively small pressure differential acting on diaphragm I will be of sufficient magnitude to open said metering valve against the liquid fuel pressure in fuel feed chamber It. The amount of liquid fuel required to flow per second even under full load is only a fraction of a cubic inch per second for many engines and under pressure, hence the metering valve may be quite small.

While the one embodiment of my invention as represented by the drawing and fully described in the foregoing specification, is a satisfactory and useful design, I do not wish to be limited to this one design. Many of the component parts may be altered as to size and shape and yet remain within the intended scope of my invention.

I do not wish to be limited in any manner by the selection of materials, since that point is merely a matter of experience and choice. Many materials, as long as they are not acted upon by liquid or fuel vapors or air mixtures, may be satisfactory.

I claim:

A liquid feed carburetor comprising an air inlet tube, a main throttle valve in the air inlet tube, a venturi in the air inlet.tube upstream of the main throttle valve, a fuel passage extending through the wall of the air inlet tube at the throat portion of the venturi communicating with a source of fuel supply under pressure, an air passage extending through the air inlet tube at the throat portion of the venturi in alignment with said fuel passage communicating with an air pressure chamber, a variable opening fuel valve for controlling flow of fuel through said fuel passage, force transmitting means connected 1 to the fuel valve and extending through said fuel and air passages, pressure responsive means in said air pressure chamber operably connected with the force transmitting means and tending to increase the opening of the fuel valve on increase of air flow through said venturi, a restriction in said fuel passage, pressure responsive means operably connected with the forge.

transmitting means responsive to pressure differential induced by fuel flow past said restriction and tending to decrease the opening of the fuel valve on increase of fuel flow past said restriction, spring means connected with said force transmitting means tending to close said fuel valve, a conduit connecting said air pressure inlet tube downstream of in said chamber for idling and adjustable valve means for controlling air flow through said conduit.

OWEN L. GARRETSON. 

